Fuse



E. o. KRIEGSTEDT 1,927,371

' FUSE Filed Jan. 15, 1952' gimme Mp5 v a? W K? M; M

Patented Sept. 19, 1933 UNITED STATES PATENT OFFICE Application January15, 1932. Serial No. 586,719

The present invention relates to electric fuses and more particularly tofuses of the cartridge type having amongst its principal objects toprovide an attachment for such, as will permit of the more readyhandling of the fuses, especially when inserting or withdrawing the samefrom its connection within an electrical circuit, in which it is to beused.

- One very important object of this invention is to provide a novelsignalling device in connection with such a fuse, the device being inthe form of a miniature lamp which is caused to glow whenever the fuseelement is fused or blown" by excess current, and it is to be noted thatthis lamp thus immediately indicates to a repair man which fuse of anumber of fuses is to be replaced.

A further object of the present invention is to provide a combined pilotlight housing and handle for fuses of the cartridge type, which will notonly permit of the safe handling of the fuse when connecting the samewithin an electric circuit, but which has within the housing asignalling member capable of visibly indicating when the fusible elementof the fuse has been ruptured.

With the above and other objects in view as will be hereinafterapparent, the invention consists in general of certain novel details ofconstruction and combinations of parts hereinafter fully described,illustrated in the accompanying drawing and specifically claimed In theaccompanying drawing like characters of reference indicate like parts inthe several views, and:

Figure 1 is a side elevation of the improved fuse.

Figure 2 is an end view thereof.

Figure 3 is a longitudinal sectional view of the same.

Figure 4 is an end view of the fuse with the covering cap adjacent theobserver removed.

In the embodiment of the invention as herein disclosed there is provideda body including a central tubular portion 10 which is made of somesuitable insulating material. Each end of this portion 10 is externallythreaded and on each of these threaded ends is screwed a metallic nippleor inner cap 11 having its outer end reduced and closed by a diaphragm12 except that each diaphragm is provided with a pair of parallel slots13. Furthermore, the tube 10 is provided with a lateral vent opening 14.The outer end of each inner cap 11 is externally threaded and on cap 15which has a knurled periphery so that under normal conditions it may bescrewed on or 011 its inner cap by gripping with the fingers. However, ascrew kerf 16 is provided for the outer cap so that a screw driver maybe used in case the covering cap sticks and cannot be worked by thefingers. A fusible strip 18 of the usual soft alloy metal is positionedin the tube 10 with each end extending through a slot 13 of a respectiveinner cap 11 and is bent at its ends so that these ends are clampedbetween the covering caps 15 and 05 the inner caps 11 as shown best inFigure 3.

By means of this arrangement the strip 18'may be readily renewed at anytime since all that is necessary is to unscrew the caps 15 and, afterremoving the old strip, thread a piece of fuse strip through respectiveslots. One end is then bent over and held by replacing the covering capat that end. The strip may then be pulled tight, bent over and cut off.Finally the remaining covering cap is screwed on. Thus the active oruseful length of the replacement will be equal to that of the stripwhich is replaced and the fuse will accordingly always have the samecapacity so long as the fuse strip is of the same cross-sectional area.Moreover, the capacity of this fuse may be varied at will by using fusestripping of desired cross-section. The foregoing description taken inconnection with the drawing. discloses a cartridge type of fuse which isnow in general use, but the invention has reference to a pilot light orindicator for this type of fuse, which will now be described.

The lamp body or housing consists of a central tubular portion 19 havinga metallic cap 20 on each end and these caps are brazed or otherwiseconductively fixed to the respective inner caps 11. By so permanentlyfixing the lamp housing 19 to the fuse casing 10, the former willproject beyond the clips of the fuse block (not shown) when the fuse isconnected to the latter, thereby 9 not only providing a lamp housing buta projecting handle by which an operator may easily and readily takehold of the fuse for withdrawing the same from the clips of the fuseblock. A sight window 21 is provided in the tube 19 on the side remotefrom the tube 10. 'In the tube 19 opposite the window 21 is a miniaturelamp 22 which has one terminal connected by a conductor 23 to one of thecaps 20 while the other terminal of the lamp is connected by a conductor24, having a resistance element 25 interposed in its length, to theremaining cap 20. The miniature lamp or other luminous indicating meansindicated by the numeral 22 uponthe drawing, is preferably a smallsealed glass tube charged with gas under pressure and provided withsuitable electrodes, the gas being of a character that produces aluminous glow when anelectric current is passed therethrough, thepressure of the gas and the spacing of the electrodes being determinedby the voltage to be impressed on the electrodes, and having a currentlimiting resistance in series with one of the electrodes. The tubeherein shown is preferably designed so that it will glow with a currentof four microamperes, said amount being amply provided by an alternatingcurrent circuit having a capacity of .301 mi. The resistance 25 issuflicient to cause substantially all of the current of the cirsuit inwhich the fuse is used to flow through the strip 18 so long as thelatter is intact. However, if the strip 18 is fused then suflicientcurrent will flow through the resistance and lamp to cause the latter toglow, thus giving a visible indication of the blowing of the fuse.

Should a short circuit occur in the electrical circuit in which thisfuse is included, the fuse element 18 will first blow or be rupturedwhereupon the current will be directed through the resistance 25 and thelamp 22 and the latter giving off a. glow indicating that the fuseelement has been blown. This lamp will continue to glow even after thecause of the short circuit is removed and the electrical circuit againstopened due to the fact that the lamp 22 has such a small currentconsumption. The resistor 25 not only protects the lamp 22 fromexcessive current flowing therethrough but obviously will protect anydelicate instruments that may be included.

in the electrical circuit. The lamp 22 draws its energy through acapacity effect, and accordingly, will continue to flow even after thecause of the 31101 t circuit is removed and the circuit is open.

As the lamp body or housing 19 is permanently attached and separatedfrom the housing or casing 10 of the fuse, it may be utilized in thehandle for causing the cartridge fuse to be inserted within or withdrawnfrom the terminal clip of the electric circuit in which it is to beused, thereby preventing the operator from coming in contact with theterminals of the electric circuit and protecting him against injury.

There has thus been provided a simple and eflicient device of the kinddescribed and for the purpose specified.

It is obvious that minor changes may be made in the form andconstruction of the invention without departing from the material spiritthereof. It is not, therefore, desired to confine the invention to theexact form herein shown and described, but it is desired to include allsuch as properly come within the scope claimed.

Having thus described the invention, what is claimed as new, is:

A fuse unit comprising a casing, contact terminals arranged at the outerends of said casing, a fusible element housed within said casing andelectrically connected to said contact terminals, a side extensionpermanently secured to said casing, said side extension being retainedin spaced relation to said casing and constituting a handhold, said sideextension being formed with a sight opening, a glow lamp positionedwithin said side extension, a resistor located within said sideextension, and independent means in parallel with said fusible elementfor connecting said glow lamp and resistor in series with said terminalswhereby the rupture of the fusible element may be visibly indicatedthrough the sight opening of said side extension.

CARL E. O. KRIEGSTEDT.

